Embodiments of the inventive concept relate generally to semiconductor technology. More particularly, embodiments of the inventive concept relate to semiconductor memory devices and memory systems incorporating the semiconductor memory devices.
Dynamic random access memory (DRAM) is a common form of semiconductor memory. DRAM is commonly used for temporary data storage in electronic devices such as computing and telecommunication devices, as well as many others. DRAM has a number of desirable characteristics, including relatively low cost and high storage density.
A DRAM comprises a plurality of memory cells each comprising a capacitor for storing data and an access transistor for controlling access to the stored data. The plurality of memory cells are typically arranged in memory blocks that can be controlled independent of each other. The memory blocks are controlled by a plurality of control signals to perform functions such as read, write, and refresh operations. The control signals can comprise, for instance, row address strobe (RAS) signals, column address strobe (CAS) signals, and others.
Many of the control signals are characterized by parameters that vary according to different operating characteristics of different memory blocks. For instance, memory blocks containing leaky capacitors or other defects may need to be refreshed more frequently than memory blocks without defects, requiring certain control signals to use different timing parameters.